Cosmological Surveys Research Articles

Cosmic Tidal Reconstruction with Halo Fields

Abstract The gravitational coupling between large-scale perturbations and small-scale perturbations leads to anisotropic distortions of the small-scale matter distribution. The measured local small-scale power spectrum can thus be used to infer the large-scale matter distribution. In this paper, we present a new tidal reconstruction algorithm for reconstructing large-scale modes using the full three-dimensional tidal shear information. We apply it to simulated dark matter halo fields and find the reconstructed large-scale density field correlates well with the original matter density field on large scales, improving upon the previous tidal reconstruction method, which only uses two transverse shear fields. This has profound implications for recovering lost 21 cm radial modes due to foreground subtraction and constraining primordial non-Gaussianity using the multitracer method with future cosmological surveys.

100 years of mathematical cosmology: Models, theories, and problems, Part A.

An elementary survey of mathematical cosmology is presented. We cover certain key ideas and developments in a qualitative way, from the time of the Einstein static universe in 1917 until today. We divide our presentation into four main periods, the first one containing important cosmologies discovered until 1960. The second period (1960–80) contains discussions of geometric extensions of the standard cosmology, singularities, chaotic behaviour and the initial input of particle physics ideas into cosmology. Our survey for the third period (1980–2000) continues with brief descriptions of the main ideas of inflation, the multiverse, quantum, Kaluza-Klein and string cosmologies, wormholes and baby universes, cosmological stability and modified gravity. The last period that ends today includes various more advanced topics such as M-theoretic cosmology, braneworlds, the landscape, topological issues, the measure problem, genericity, dynamical singularities and dark energy. We emphasize certain threads that run throughout the whole period of development of theoretical cosmology and underline their importance in the overall structure of the field. This is Part A of our survey covering the first two periods of development of the subject. The second part will include the third and fourth periods. We end this outline with an inclusion of the abstracts of all papers contributed to the Philosophical Transactions of the Royal Society A theme issue, ‘The Future of Mathematical Cosmology’.This article is part of the theme issue ‘The future of mathematical cosmology, Volume 1’.

Do current observations support transient acceleration of our universe?

In this paper, we have investigated a very natural question regarding the dynamics of the universe, namely, the possibility of its decelerating phase immediately after the present accelerating phase. To begin with, we have focused on the matter creation theory which is considered to be a viable alternative to dark energy and modified gravity models. Moreover, we have introduced the cosmographic approach which allows us to express the free parameters of a cosmological model in terms of the known cosmographic parameters. Assuming a generalized matter creation rate, we have discussed the theoretical bounds on the model parameters allowing the future deceleration of the universe. Moreover, using the observational bounds on the cosmographic parameters obtained from the low redshifts observational probes, we have also examined the chance of a decelerating phase of the universe. Finally, considering a variety of known cosmological models and parametrizations, we have tested the same possibility. Our analysis shows that the chance of a future decelerating expansion of the universe is highly dependent on the choice of the cosmological models and parametrizations and also on the observational data. Even though the future decelerating expansion is allowed in some cosmological frameworks, but we do not see any strong evidence in favor of this. Perhaps, the future cosmological surveys could offer some more information regarding the fate of the universe.

Fitting AGN/Galaxy X-Ray-to-radio SEDs with CIGALE and Improvement of the Code

Abstract Modern and future surveys effectively provide a panchromatic view for large numbers of extragalactic objects. Consistently modeling these multiwavelength survey data is a critical but challenging task for extragalactic studies. The Code Investigating GALaxy Emission (cigale) is an efficient python code for spectral energy distribution (SED) fitting of galaxies and active galactic nuclei (AGNs). Recently, a major extension of cigale (named x-cigale) has been developed to account for AGN/galaxy X-ray emission and improve AGN modeling at UV-to-IR wavelengths. Here, we apply x-cigale to different samples, including Cosmological Evolution Survey (COSMOS) spectroscopic type 2 AGNs, Chandra Deep Field-South X-ray detected normal galaxies, Sloan Digital Sky Survey quasars, and COSMOS radio objects. From these tests, we identify several weaknesses of x-cigale and improve the code accordingly. These improvements are mainly related to AGN intrinsic X-ray anisotropy, X-ray binary emission, AGN accretion-disk SED shape, and AGN radio emission. These updates improve the fit quality and allow for new interpretation of the results, based on which we discuss physical implications. For example, we find that AGN intrinsic X-ray anisotropy is moderate, and can be modeled as L X ( θ ) ∝ 1 + cos θ , where θ is the viewing angle measured from the AGN axis. We merge the new code into the major branch of cigale, and publicly release this new version as cigale v2022.0 on https://cigale.lam.fr.

A prediction for anisotropies in the nearby Hubble flow

We assess the dominant low-redshift anisotropic signatures in the distance-redshift relation and redshift drift signals. We adopt general-relativistic irrotational dust models allowing for gravitational radiation — the `quiet universe models' — which are extensions of the silent universe models. Using cosmological simulations evolved with numerical relativity, we confirm that the quiet universe model is a good description on scales larger than those of collapsing structures. With this result, we reduce the number of degrees of freedom in the fully general luminosity distance and redshift drift cosmographies by a factor of ∼ 2 and ∼ 2.5, respectively, for the most simplified case. We predict a dominant dipolar signature in the distance-redshift relation for low-redshift data, with direction along the gradient of the large-scale density field. Further, we predict a dominant quadrupole in the anisotropy of the redshift drift signal, which is sourced by the electric Weyl curvature tensor. The signals we predict in this work should be tested with present and near-future cosmological surveys.

Cosmic backgrounds from the radio to the far-infrared: Recent results and perspectives from cosmological and astrophysical surveys

Cosmological and astrophysical surveys in various wavebands, in particular from the radio to the far-infrared, offer a unique view of the universe’s properties and the formation and evolution of its structures. After a preamble on the so-called tension problem, which occurs when different types of data are used to determine cosmological parameters, we discuss the role of fast radio bursts in cosmology, in particular for the missing baryon problem, and the perspectives from the analysis of the 21 cm redshifted line from neutral hydrogen. We then describe the Planck Legacy Archive, its wealth of scientific information and next developments, and the promising perspectives expected from higher resolution observations, in particular for the analysis of the thermal Sunyaev–Zel’dovich effect. Three cosmological results of the Planck mission are presented next: the implications of the map of Comptonization fluctuations, the dipole analysis from cross-correlating cosmic microwave background anisotropy and Comptonization fluctuation maps, and the constraints on the primordial tensor-to-scalar perturbation ratio. Finally, we discuss some future perspectives and alternative scenarios in cosmology, such as the study of the Lorentz invariance violation with the cosmic microwave background polarization, the introduction of new gravitational degrees of freedom to solve the dark matter problem, and the exploitation of the magnification bias with high-redshift sub-millimeter galaxies to constrain cosmological parameters.

Cosmic Voids and BAO with relative baryon-CDM perturbations

ABSTRACT We study the statistics of various large-scale structure tracers in gravity-only cosmological simulations including baryons and cold dark matter (CDM) initialized with two different transfer functions, and simulated as two distinct fluids. This allows us to study the impact of baryon-CDM relative perturbations on these statistics. In particular, we focus on the statistics of cosmic voids, as well as on the matter and halo real-space 2-point correlation function and baryon acoustic oscillations (BAO) peak. We find that the void size function is affected at the 1–2 per cent level at maximum, and that the impact is more important at higher redshift, while the void density profile and void bias are roughly unaffected. We do not detect a sizeable impact of relative baryon-CDM perturbations on the real-space correlation functions of matter and haloes or the BAO peak, which is in line with results from previous works. Our results imply that it would be hard to use voids or real-space correlation functions to constrain baryon-CDM relative perturbations, but also that we might not have to include them in models for the analysis of future cosmological surveys data.

Mock catalogues of emission-line galaxies based on the local mass density in dark-matter only simulations

ABSTRACT The high-precision measurement of spatial clustering of emission-line galaxies (ELGs) is a primary objective for upcoming cosmological spectroscopic surveys. The source of strong emission of ELGs is nebular emission from surrounding ionized gas irradiated by massive short-lived stars in star-forming galaxies. As a result, ELGs are more likely to reside in newly formed haloes and this leads to a non-linear relation between ELG number density and matter density fields. In order to estimate the covariance matrix of cosmological observables, it is essential to produce many independent realizations to simulate ELG distributions for large survey volumes. To this end, we present a novel and fast scheme to populate ELGs in dark-matter only N-body simulations based on local density field. This method enables fast production of mock ELG catalogues suitable for verifying analysis methods and quantifying observational systematics in upcoming spectroscopic surveys and can populate ELGs in moderately high-density regions even though the halo structure cannot be resolved due to low resolution. The power spectrum of simulated ELGs is consistent with results of hydrodynamical simulations up to fairly small scales ($\lesssim 1 h \, \mathrm{Mpc}^{-1}$), and the simulated ELGs are more likely to be found in filamentary structures, which is consistent with results of semi-analytic and hydrodynamical simulations. Furthermore, we address the redshift-space power spectrum of simulated ELGs. The measured multipole moments of simulated ELGs clearly exhibit a weaker Finger-of-God effect than those of matter due to infalling motions towards halo centre, rather than random virial motions inside haloes.

Validating Synthetic Galaxy Catalogs for Dark Energy Science in the LSST Era

Large simulation efforts are required to provide synthetic galaxy catalogs for ongoing and upcoming cosmology surveys. These extragalactic catalogs are being used for many diverse purposes covering a wide range of scientific topics. In order to be useful, they must offer realistically complex information about the galaxies they contain. Hence, it is critical to implement a rigorous validation procedure that ensures that the simulated galaxy properties faithfully capture observations and delivers an assessment of the level of realism attained by the catalog. We present here a suite of validation tests that have been developed by the Rubin Observatory Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC). We discuss how the inclusion of each test is driven by the scientific targets for static ground-based dark energy science and by the availability of suitable validation data. The validation criteria that are used to assess the performance of a catalog are flexible and depend on the science goals. We illustrate the utility of this suite by showing examples for the validation of cosmoDC2, the extragalactic catalog recently released for the LSST DESC second Data Challenge.

Hydrogen Intensity and Real-Time Analysis Experiment: 256-element array status and overview

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a radio interferometer array currently in development, with an initial 256-element array to be deployed at the South African Radio Astronomy Observatory (SARAO) Square Kilometer Array (SKA) site in South Africa. Each of the 6m, $f/0.23$ dishes will be instrumented with dual-polarisation feeds operating over a frequency range of 400-800 MHz. Through intensity mapping of the 21 cm emission line of neutral hydrogen, HIRAX will provide a cosmological survey of the distribution of large-scale structure over the redshift range of $0.775 < z < 2.55$ over $\sim$15,000 square degrees of the southern sky. The statistical power of such a survey is sufficient to produce $\sim$7 percent constraints on the dark energy equation of state parameter when combined with measurements from the Planck satellite. Additionally, HIRAX will provide a highly competitive platform for radio transient and HI absorber science while enabling a multitude of cross-correlation studies. In this paper, we describe the science goals of the experiment, overview of the design and status of the sub-components of the telescope system, and describe the expected performance of the initial 256-element array as well as the planned future expansion to the final, 1024-element array.

The Three Hundred project: Contrasting clusters galaxy density in hydrodynamical and dark matter only simulations

Cluster number count is a major cosmological probe for the next generation of cosmological large scale-structure surveys like the one expected from the Euclid satellite mission. Cosmological constraints will be mainly limited by the understanding of the selection function (SF), which characterize the probability of detecting a cluster of a given mass and redshift. The SF can be estimated by injecting realistic simulated clusters into the survey and re-applying the detection procedure. For this purpose we intend to use The Three Hundreds project, a 324 cluster sample simulated with full-physics hydrodynamical re-simulations. In this paper we concentrate on the study of the distribution of member galaxies in the cluster sample. First, we study possible resolution effects by comparing low and high resolution simulations. Finally, accounting for the latter we derive the density profiles of the member galaxies and discuss their evolution with cluster mass and redshift.

Euclidpreparation

We present a machine learning framework to simulate realistic galaxies for theEuclidSurvey, producing more complex and realistic galaxies than the analytical simulations currently used inEuclid. The proposed method combines a control on galaxy shape parameters offered by analytic models with realistic surface brightness distributions learned from realHubbleSpace Telescope observations by deep generative models. We simulate a galaxy field of 0.4 deg2as it will be seen by theEuclidvisible imager VIS, and we show that galaxy structural parameters are recovered to an accuracy similar to that for pure analytic Sérsic profiles. Based on these simulations, we estimate that theEuclidWide Survey (EWS) will be able to resolve the internal morphological structure of galaxies down to a surface brightness of 22.5 mag arcsec−2, and theEuclidDeep Survey (EDS) down to 24.9 mag arcsec−2. This corresponds to approximately 250 million galaxies at the end of the mission and a 50% complete sample for stellar masses above 1010.6 M⊙(resp. 109.6 M⊙) at a redshiftz ∼ 0.5 for the EWS (resp. EDS). The approach presented in this work can contribute to improving the preparation of future high-precision cosmological imaging surveys by allowing simulations to incorporate more realistic galaxies.

Photometric Objects around Cosmic Webs (PAC) Delineated in a Spectroscopic Survey. I. Methods

Abstract We provide a method for estimating the projected density distribution n ¯ 2 w p ( r p ) of photometric objects around spectroscopic objects in a spectroscopic survey. This quantity describes the distribution of photometric sources with certain physical properties (e.g., luminosity, mass, and color) around cosmic webs (PAC) traced by the spectroscopic objects. The method can make full use of current and future deep and wide photometric surveys to explore the formation of galaxies up to medium redshift (z s &lt; 2) 3 3 Throughout the paper, we use z s for redshift, z for the z-band magnitude, z p for the photometric redshift. with the aid of cosmological spectroscopic surveys that sample only a fairly limited species of objects (e.g., emission line galaxies). As an example, we apply the PAC method to the CMASS spectroscopic and HSC-SSP PDR2 photometric samples to explore the distribution of galaxies for a wide range of stellar masses from 109.0 to 1012.0 M ⊙ around massive galaxies at z s ≈ 0.6. Using the abundance-matching method, we model n ¯ 2 w p ( r p ) in N-body simulation using Markov chain Monte Carlo sampling, and we accurately measure the stellar–halo mass relation and stellar mass function for the whole mass range. We can also measure the conditional stellar mass function of satellites for central galaxies of different mass. The PAC method has many potential applications for studying the evolution of galaxies.

Constraining Gravity with Synergies between Radio and Optical Cosmological Surveys

Constraining Gravity with Synergies between Radio and Optical Cosmological Surveys

Galaxy cluster number counts with individual lensing mass estimates: Forecasts for Euclid

The ΛCDM model is gradually becoming challenged by observational data. Upcoming cosmological surveys will increase the number of detected galaxy clusters by several orders of magnitude. Therefore, clusters will shortly provide precise cosmological constraints and improve our understanding of structure formation in the Universe. In the following, we present a cluster likelihood based on individual weak lensing mass estimates and forecast Euclid’s performances within this framework. We use a matched filter for weak lensing mass estimation and model its characteristics with a set of simulations. We use the Flagship N-body simulation to emulate the expected cluster mass distribution of a Euclid-like sample and test our statistical framework against it. Finally, we simultaneously constrain the observable-mass relation and the cosmological parameters.

Cosmological Tests of Gravity: A Future Perspective

In this review, we outline the expected tests of gravity that will be achieved at cosmological scales in the upcoming decades. We focus mainly on constraints on phenomenologically parameterized deviations from general relativity, which allow to test gravity in a model-independent way, but also review some of the expected constraints obtained with more physically motivated approaches. After reviewing the state-of-the-art for such constraints, we outline the expected improvement that future cosmological surveys will achieve, focusing mainly on future large-scale structures and cosmic microwave background surveys but also looking into novel probes on the nature of gravity. We will also highlight the necessity of overcoming accuracy issues in our theoretical predictions, issues that become relevant due to the expected sensitivity of future experiments.

The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) Survey Design, Reductions, and Detections*

Abstract We describe the survey design, calibration, commissioning, and emission-line detection algorithms for the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX). The goal of HETDEX is to measure the redshifts of over a million Lyα emitting galaxies between 1.88 &lt; z &lt; 3.52, in a 540 deg2 area encompassing a comoving volume of 10.9 Gpc3. No preselection of targets is involved; instead the HETDEX measurements are accomplished via a spectroscopic survey using a suite of wide-field integral field units distributed over the focal plane of the telescope. This survey measures the Hubble expansion parameter and angular diameter distance, with a final expected accuracy of better than 1%. We detail the project’s observational strategy, reduction pipeline, source detection, and catalog generation, and present initial results for science verification in the Cosmological Evolution Survey, Extended Groth Strip, and Great Observatories Origins Deep Survey North fields. We demonstrate that our data reach the required specifications in throughput, astrometric accuracy, flux limit, and object detection, with the end products being a catalog of emission-line sources, their object classifications, and flux-calibrated spectra.

Cosmological radiation density with non-standard neutrino-electron interactions

Non-standard interactions (NSI) between neutrinos and electrons can significantly modify the decoupling of neutrinos from the plasma. These interactions have two effects on the overall picture: (i) they alter neutrino oscillations though matter effects and (ii) they modify the scattering and annihilation processes involving neutrinos and electrons and positrons. We study the role of non-universal and flavour-changing NSI in the decoupling and how they impact the determination of the effective number of neutrinos, N eff. We examine the degeneracies between NSI parameters and we compare the expected sensitivity from future cosmological surveys with the current limits from terrestrial experiments. We outline the complementarity between both approaches.

Multi-wavelength spectroscopic probes: biases from neglecting light-cone effects

Next-generation cosmological surveys will observe larger cosmic volumes than ever before, enabling us to access information on the primordial Universe, as well as on relativistic effects. In a companion paper, we applied a Fisher analysis to forecast the expected precision on f NL and the detectability of the lensing magnification and Doppler contributions to the power spectrum. Here we assess the bias on the best-fit values of f NL and other parameters, from neglecting these light-cone effects. We consider forthcoming 21cm intensity mapping surveys (SKAO) and optical galaxy surveys (DESI and Euclid), both individually and combined together. We conclude that lensing magnification at higher redshifts must be included in the modelling of spectroscopic surveys. If lensing is neglected in the analysis, this produces a bias of more than 1σ — not only on f NL, but also on the standard cosmological parameters.

A Fast and Accurate Analytic Method of Calculating Galaxy Two-point Correlation Functions

Abstract We have developed a new analytic method to calculate the galaxy two-point correlation functions accurately and efficiently, applicable to surveys with finite, regular, and mask-free geometries. We have derived simple, accurate formulas of the normalized random–random pair counts RR as functions of the survey area dimensions. We have also suggested algorithms to compute the normalized data-random pair counts DR analytically. With all edge corrections fully accounted for analytically, our method computes RR and DR with perfect accuracy and zero variance in O(1) and O(N g) time, respectively. We test our method on a galaxy catalog from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) simulation. Our method calculates RR + DR at a speed 3–6 orders of magnitude faster than the brute-force Monte Carlo method and 2.5 orders of magnitude faster than tree-based algorithms. For a galaxy catalog with 10 million data points in a cube, this reduces the computation time to under 1 minute on a laptop. Our analytic method is favored over the traditional Monte Carlo method whenever applicable. Some applications in the study of correlation functions and power spectra in cosmological simulations and galaxy surveys are discussed. However, we recognize that its applicability is very limited for realistic surveys with masks, irregular shapes, and/or weighted patterns.